I briefly blogged yesterday about the massive image of our own galaxy, the milky way, that has been released by the people using the infrared Spitzer Space Telescope.
I just wanted to reiterate that it is really worth taking a look, and there is a great site produced by the team that not only uses the Google Maps interface (.astronomy!) but also highlights some features like nebulae to help the uninitiated viewer.
Galaxy Zoo has put up a sort of thank you poster to all its volunteers. The names listed are those people who, when signing up to Galaxy Zoo, gave permission for their names to be published. There are a lot of names, including some funny ones. It’s worth taking a look.
I always wondered where they get all the antimatter to power the starships in Star Trek. Maybe they get it from the centre of the galaxy. New results from NASA’s INTEGRAL spacecraft, which tracks gamma ray emissions, may have explained the origin of the cloyd of antimatter that seems to be hanging around the centre of the Milky Way, our galaxy.
Originally discovered in the 1970s, the giant cloud of antimatter is 10,000 light years across and gives off te energy of 10,000 Suns, only it shines in the gamma-ray part of the electromagnetic spectrum (it is shown above). Only, no one could explain how it got there, or how it continued to exists, when it ought to be annihilated by all the matter in the region.
It had been suggested that the cloud was the result of dark matter reacting either with itself, or with regular matter. INTEGRAL scientists have deduced the shape of the cloud however, and this has given them the vital clue to deducing the origins of the cloud. Also skewed the the right of the galactic centre are a certain type of binary star system, known as hard low-mass X-ray binaries. These produce positrons and there seem to be enough of them to “suggest that about half and possibly all the antimatter is coming from [the] X-ray binaries”.
I love NASA’s Astronomy Picture of the Day, known to its friends as APOD. So to honour that Great website, which has been running for more than a decade, I here present my own personal top ten list of APODs. They may not be quite the same as anyone else Top Ten but they represent some of the best things about the APOD site as well as being some of the most impressive images.
10: Mars Then and Now
Two images of Mars taken over 100 years apart. The first was drawn by Eugene Antoniadi in 1894, the second is from Hubble during the close approach of Mars in 2003. Its interesting to see what they got right and what they got wrong. Notably the extensive system of Martian Canals, which Percival Lowell was so adamant existed and proved the presence of Martians.
Credit: Tom Ruen, Eugene Antoniadi, Lowell Hess, Roy A. Gallant, HST, NASA
More Historical APODs - Yuri Gagarin, Voynich Manuscript
9: The Surface of Europa
Back in January 1998, when this image appeared on APOD, the Galileo Mission was still sending back amazing new pictures from Jupiter and it’s Moons. This was around the time I first discovered APOD and have been checking it ever since.
Credit: Galileo Project, JPL, NASA
More Groundbreaking APODs - Shadow of Saturn, Pluto’s True Colours
8: Bubble vs Cloud
This 2005 APOD captured my imagination for some reason. You can really see a three-dimensional effect in this beautiful picture. The actual title of the image is ‘ NGC 7635: The Bubble Nebula’ but the phrase ‘Bubble vs Cloud’ stuck with me somehow. It just got me thinking about how dynamic all of these giant objects are, even if we will never see it for ourselves.
Credit: Russell Croman
More APOD Nebulae - The Eagle Nebula, Orion Nebula, Carina Nebula
7: Close Up of the Face on Mars
After years of being told by people that there was a giant human face on Mars that an ancient civilisation had once created it was satisfying to see it for real and notice that ‘hey, there is no face’.
Credit: Malin Space Science Systems, MGS, JPL, NASA
More Debunking APODs - Equinox Eggs, Green Flash, The Moon Illusion
6: Binary Black Hole
This composite image shows the x-ray in blue and the radio in pink. You can see two black holes in the middle, which are each streaming out relativistic particles. These two objects are 300 million light years away! This APOD from April 2006 was the first time I had ’seen’ a black hole in any convincing sense.
Credit: X-Ray: NASA/CXC/D.Hudson, T.Reiprich et al. (AIfA); Radio: NRAO/VLA/NRL
More Unseeable APODs - Dark Matter, Neutrinos
5: A Sun Pillar
One of the things APOD does best is show not only planets, nebulae and other distant objects, but also some cool, Earth-bound astronomical tit-bits. This Sun Pillar is created by ice crystals in the atmosphere. They are best seen during the colder months.
Credit: Stan Richard
More Earthbound APODs - Giant Machine, Lenticular Clouds, Aurora
4: Earthrise
This is a Christmas Eve APOD from 2004. The site has never been afraid to put up historical pictures or to be a little poetic when it feels like it. This image was taken around ChristmasEve when the three Apollo 8 astronauts were orbiting the Moon. They returned safely on December 27th, in time to see the 1967 Sunrise back on the Earth.
Credit: Apollo 8, NASA
More Poetic APODs - Martian Love, Huygens Discovery, Liberty Bell
3: Hyperion
Like a 250km sponge, Saturn’s Moon Hyperion is covered in odd craters and has a density so low that it has led researchers to assume it made up of vast deep caverns. This image shows the moon in excellent detail. The images on APOD have steadily improved with improving technology over the years and this amazing Hyperion picture is a great example.
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
More High Resolution APOD - Annual Eclipse, Mars HiRISE, ISS Silhouette
2: Blue Lagoon
Sometimes you see a picture that just takes your breath away. This APOD was just such a picture. This wonderful Lagoon Nebula picture, which to me, looks like a painting, was not taken by Hubble as many might think but by a 20″ telescope on Earth.
Credit: Russell Crowman
More Artistic APODs - Moon from Space, Sombrero in IR
1: Venus Near the Moon
Not a grand finale in one sense, but a stunning picture never-the-less. What APOD has always done best are images like these, taken not by massive telescopes but by normal observers with affordable equipment. The stuff you can see with your eyes and appreciate instantly without explanation. This crisp, detailed image of Venus near the Moon sums up what so many of us like about astronomy, and why the subject remains accessible to just about anyone.
Credit: Jay Ouellet
More Backyard APOD - Moon Animation, Station and Shuttle, Blue Moon
So thank you to Astronomy Picture of the Day for many years of service to the internet. May you long continue to wow us on a daily basis.
APOD is also available as a Google Homepage Gadget, a Netvibes Module, an Apple Dashboard Widget, a Wordpress Widget, a Yahoo Widget, a Windows Vista Gadget , as a Twitter Feed and probably loads more.
If you have other APODs you think deserve attention, leave a link in the comments thread so we can all see.
I recently saw a Digg article which linked to a space.com page about the 10 Strangest Things in Space. All but 2 of the items were not pictures at all but computer simulations, or artists impressions. So here to correct this injustice to phenomena everywhere I present the REAL 10 Strangest Things in Space - or at least in my opinion. Feel free to suggest any others in the comments.
V838 Monoceroti Expansion (Hubble)
It wasn’t anything interesting until it happened but the star V838 Monoceroti, which had simply sat in obscurity, flared up in 2002 to become 600,000 more luminous than our own Sun. It didn’t take long for the star to fade back into the darkness but the Hubble Space Telescope managed to get quite a few pictures of it during its active phase. (Click for animated version)
In this series of images you can see how the star’s outer layers were first expelled and then cut away by the powerful radiation from the star. The event was made even more interesting by the fact that a ‘light echo‘ was seen. During the expansion the object appeared to expand faster than the speed of light - the effect was however merely an astronomical optical illusion.
The Egg Nebula (Hubble)
Also known as CRL2688, the Egg Nebula shows a pair of mysterious ’searchlights’ bursting out from a dense cocoon of dust surrounding a hidden, Sun-like star. We see the light escaping in the directions where the cocoon is thinner. Objects like CRL2688 are rare because they are in a phase of their evolution that is short-lived. Images like this one are very important to understanding how stars like our Sun will ultimately die.
The Sun in UV (SOHO)
The surface of the Sun is far more active than most people would think. This ultraviolet video taken by NASA’s SOHO spacecraft gives brilliant detail. It allows us to see one full revolution of the Sun on its axis, which normally takes about 25 days. In this video you can make out large flares erupting from the surface and the striking magnetic loops that seem to whirl about them as they go. (Full 512×512 MPEG Here)
Red Square Nebula Nebula (Hale/Keck)
Discovered in 2007, this ruby-like nebula may be the result of two interacting stars. If one star is dying then the material from it may be dragged into a disc around the orbits of both objects. Material can then only escape from the system along the poles of the disc, resulting in two cones leading out of the stars. When viewed from the edge these cones seem like two triangles. Here the system is seen in the infrared. Structures like this are rarely seen in nebula but there is in fact a Red Rectangle Nebula which is less symmetric but still quite interesting to look at.
Abell 39 (NOAO)
Here we see an almost perfect planetary nebula that sits about 7,000 light years away in the constellation Hercules. The dot at the centre is the original star, which - as it died - released the expanding gas shell also seen clearly here. The ghostly appearance of the shell is due to the blue-green filter used to take the image, which picks out the oxygen emitted light at 500.7nm.
Saturn’s Rings (Cassini)
This marvelous panoramic view was created by combining a total of 165 images taken by the Cassini wide-angle camera over nearly three hours on Sept. 15, 2006. Cassini was sheltered from the Sun’s glare by positioning itself behind Saturn. Ring structures are revealed here in detail as they brighten substantially at viewing angles where the Sun is almost directly behind the objects. These observations allowed Cassini to detected two new faint rings.
The Horsehead Nebula Swallowed Something (SCUBA)
Observers used the JCMT submillimetre telescope on Mauna Kea in Hawaii to take this image of the familiar Horsehead Nebula, who’s outline can be seen here. When observed at 850 microns, we are seeing the cold dust at temperatures close to absolute zero. This dust is deep inside the optical nebula normally seen, which is transparent at this wavelength. It seems from the image that the Horse has swallowed a ‘lozenge’ which is in fact a region of dense dust that may be collapsing under gravity. In fact this could be a star system in the making.
Gomez’s Hamburger (Hubble)
Arturo Gomez found this odd object in 1985 and it became known as Gomez’s Hamburger for obvious reasons. It is actually a proto-planetary nebula, an earlier version of Abell 39 perhaps. The curves of light (the bun) are reflecting light from the star which is being obscured by a thick band of dust (the burger). The whole thing is only only a fraction of a light year across and located 10,000 light years away in Sagittarius.
The Solar Spectrum (NOAO)
If you could catch a rainbow and put it under a microscope you would see that it was not a continuous blend of colours. Along the width of it would be seen, scattered irregularly, dark patches. Atoms and molecules in the Sun’s atmosphere pick out specific frequencies of light and absorb them, diminishing their intensity by comparison. This images shows the spectrum of light from the Sun stretched out to make these absorption lines visible. We use the reverse of the idea (emission lines) when we make coloured lights. For instance, we excite sodium atoms to emit a signature orange light in street lamps. In this image you can see two prominent dark bands in the yellow-orange section which are the absorption due to sodium.
The Sombrero Galaxy in Infrared (Spitzer)
By looking at things in different wavelengths we can see much more than meets the eye. This image is a perfect example. Just as with the Horsehead image above we are seeing cooler material. This time it is dust in the Sombrero galaxy. The red ring is a thick band of dust encircling the whole galaxy. In the optical, this dust ring is what gives the Sombrero its distinctive black, obscuring line.
Oddities in the Orion Nebula (Hubble)
Deep within high resolution images of the Orion Nebula taken by Hubble we can see dark blobs. When you take a closer look you can see that these are like little flattened blobs. Some show a dim, red glow at their centres, others are just dark. These are proto solar-systems.
The red glowing is a protostars attempting to burst through and the dark disks are thick dust regions where one day planets may form. 6 billion years ago, this is what our Solar System may have looked from very far away.
Just the other day I was opining about how the internet needs to get in bed with science a bit more. Well lo and behold here is a fantastic example of just such a thing: Galaxy Zoo.
I saw the link on Chris Lintott’s blog and then later on Digg, but basically this is an exercise in crowd-sourcing - harnessing the power of the multitude to perform tasks usually only done by specialists. In this case, a group of researchers need to identify about a million galaxies from the Sloan Digital Sky Survey. Computers have always been a bit rubbish an image recognition so they are asking for the population of the internet to go and do it for them - an excellent idea.
You sign up and log in, then take a test of sorts to see if you’re even remotely good at it (I don’t think you have to excel at this test). Then you are given a series of galaxies to identify. Its all explained in the tutorial on the Galaxy Zoo website and is really very easy so I would say just go give it a go. By letting everyone have a go they are maximizing their chances of getting each identification correct.
This is the sort of thing science needs more of. Projects like the folding@home concept on the PS3 and this are examples of why when we network all the people of the world together, we will be greater than the sum of our population. What a nice way for everyone to contribute to astronomy - go be an astronomer now!
If you are on Facebook, they have a Galaxy Zoo Facebook group.
A while ago I posted about the Bullet Cluster, and an image which seems to reveal the dark matter within it. Now a new image from Hubble seems to do the same thing for the galaxy cluster CL0024+17.
Now I am personally rather sceptical about the validity of images such as these, although I feel sure that we will see many more of them in the coming years. ‘Showing’ dark matter sounds to me like a dangerous business. It is, after all, dark. I would argue that releasing such images is detrimental to science and astronomy more specifically. To fool the general public into believing that something exists before you are sure of it yourself is not good science.
Now it may be beneficial to model dark matter in the way shown in these images, and this could lead to a better understanding. To release this sort of thing without warning as to the subjective nature of its content is not fair on those who would simply believe it as a photo like any other. After all how sure can anyone be that what is shown here is anything real at all? It is like deducing the nature of the wind from the way birds fly.
There is more to it that just that though. I know so many people who have no clue that many of the images they see from space are false-colour, for example. I also have to explain to people everytime I shown them Andromeda through a telescope, and look back at me confused, that the images they see from Hubble and other big observatories are enhanced, essentially doctored, to make them prettier. Do you think they will understand that this dark matter ring is simply a mathematical deduction? Will they even care?
Maybe I’m overreacting, but I do believe that one of the jobs of any scientist is to report back their findings to the public at large, who ultimately fund them. The PR guys need to get educated as to what this image and the ones that are surely coming our way soon, really mean.
Dark matter is still not a subject that we know much about. Its a mystery - and that is one very good reason it is so interesting. We cannot photograph it because we don’t know where it is. Gravitational lensing tehcniques can begin to help us locate it but don’t let’s be fooled by what the com puters give us at the end of the day. If we start to believe these images are real simply because they look real we will have strayed off the correct path and begin putting garbage into our theories. This is, as my supervisor always says, never a good thing because you end up with rubbish results; garbage in, garbage out.
You can read more over at Astronomy Picture of the Day and the Bad Astronomy Blog.
NASA’s Chandra observatory, in unison with ground-based optical telescopes, has relased details of a supernova from last September which is the brightest ever recorded. SN 2006gy exploded in galaxy NGC 1260 and was the brightest such event ever seen. NGC 1260 is 240 million light years away and the supernoa appeared to outshine the entries galaxy in both optical and x-ray wavelengths.
This event is believed to be a Type II supernova, which occur at the end of a large stars life. When a star is larger than about nine solar masses it will go through a different set of fusion reactions at the end if its life. As the hydrogen runs out, having all been converted to other elements, the stars begins to grow unstable at its centre as the heavier elements grow more and more dense and the gravitational pressure becomes unsustainable by the star’s newlty formed iron core. When the core reaches a mass known as the Chandrasekhar limit, a catastrophic collapse ensues during which the stars outer layers fall inward at a speed nearly one quarter that of light.
In just a few seconds 1040 joules (one hundred billion trillion trillion trillion) of gravitational energy are crushing down on the core which becomes as desne as an atomic nuceus and so the collapse bounces. Bounce is a very gentle word for what happens but since the core has taken all the pressue it possible can, the falling material has no choice but to rebound and it blows outward, destroying the star with it and showering the universe in neutrinos and everything else.
In the above image, taken from NASA’s press release, the top section shows an artists impression of the event close-up. The lower left panel is an infrared image and the lower-right an x-ray image from Chandra. both the lower panels show the nucelus of NGC 1260 on the left and SN 2006gy on the right.
SN 2006gy is thought to be the largest such event witnessed and even more interestingly, it bore a striking resemblance to a star in our own galaxy just before it died. Eta Carinae was the star which appeared in Hubble’s 17th Anniversary image. SN 2006gy is thought to have beren a lot like ETa Carinae; both were enormous stars which had begun spewing out material. If Eta Carinae follows the same path as SN 2006gy then we could be in for more than just a bright light in Chandra’s field of view. Whereas SN 2006gy is 240 million light years away, Eta Carinae is only 7,500. If it did go supernova then it would be visible during the day and at night would cast shadows almost as well as the full moon.
Hopefully more information and more images will follow and with any luck Eta Carinae will give us a repeat, close-up discussion someday in the future. If it did then it would be the most fantastic event in all of modern civilisation.
The Darwin Lecture for the National Astronomy Meeting 2007 was given by Dr. Reinhard Genzel. He spoke about the black hole which sits at the centre of the Milky Way, our own galaxy.
Early infrared astronomy showed very fast motions in the central mass of the galaxy. 20 years later we still agree with these early results but now have other data which confirms the existence of Sagittarius A*, the black hole in the middle of the Milky Way.
VLBA measurements have shown that Sgr A* does not move with respect the centre of the galaxy. Observations of nearby stars orbiting Sgr A* have velocities which suggest it is a supermassive black hole. There is relatively low amounts of gas spiraling onto Sagittarius A*, perhaps because in such active regions, supernovae have blown away much of it away.
Although this is by far the closest supermassive black hole, it is still hard to study because there are many thick clouds of interstellar dust, which absorb visible light, between us and Sgr A*. Astronomers rely on X-rays, radio waves, and other wavelengths of energy to study the Milky Way’s core.
The object is 8,000 parsec away (~27,000 light years) and is thought to have a mass of around 3 million times that of the Sun. That’s big! It is believed tha this beast of a black hole holds in its gravity more than 100 of the galaxies most massive and energetic OB Stars within just a few light years and these stars may be the evidence that gives it away, as seen in this animation.
Sgr A* also has the peculiar property that it experiences a periodic burst of brightness every few hours, for an hour or so. This may be the result of it swallowing up material and releasing energy or even of objects careeering into each other as they in turn infall into this monstrous gravity guzzler.
Reinhard Genzel has been working on this object for some time, amongst other things, and so his talk on thse subject was excellent. It was a pleasure to hear someone speak on a topic that doesn’t end up being an utter mystery or controversy for a change. That’s not to say that Sgr A* is all wrapped up, because it certainly isn’t. This is an object that will remain a topic of intense study for some time and no doubt Genzel will be at the front of it.
The image above shows the Bullet Cluster. Also known as 1E 0657-56, this is a pair of clusters of galaxies some 3.4 billion light years away. As Jon Davies told us in yesterday’s Astrolunch meeting however: you should be careful about believing everything you see. This image is not a regular photograph by any means. You can see the galaxies scattered about with an orange glow. This much is familiar. Layered onto this optical data is the pink, X-Ray picture from the Chandra telescope. This pink light is actually the high energy X-Ray radiation from a hot gas that permeates the cluster. Again though it is not unusual to see two different wavelength regimes seen in the same photograph.
What is unusual is that the blue ‘light’ seen here is not photographic in nature at all. It is the location of the mass in this region deduced by weak gravitational lensing - it is not a real effect but rather a mathematical interpretation of where the mass should be. As you can see it does not line up with the visual traces of the mass that we see as light and X-Ray material.
This is because it is believed that the Bullet Cluster shows us quite nicely where the dark matter can be found in this cluster. The interpretation of this image by the researchers who have studied it is that the hot, pink gas is the energy released by ordinary matter in this pair of clusters as they have collided with one another. The energy of the collision has excited the gas to emit in the X-Ray.
However not all the mass in the region is ordinary (something believed to be true about most of the universe). Dark matter is material that has mas but doesn’t interact with other, ordinary matter by the usual routes. It does not feel magnetism, or electrical forces or emit light. But is stays tethered to the ordinary matter by gravity alone.
As these two clusters collided the dark matter passed through like an ordinary pair of gaseous objects would, where as the regular, every day material became heated and disturbed and distorted in shape.
There is a wonderful video of a simulation of this hypothetical collision which you can find here.
This lovely picture adds to the already heated debate among the astrophysical community as to the existence of dark matter.
